The Impact of Metallicity Evolution of the Universe on the Maximum Mass of LIGO Binary Black Holes

We can be biased against observing massive black holes (BHs) merging in the local universe as the bounds on the maximum BH mass (${M}_{\mathrm{BH}}^{\max }$) depends on the assumptions regarding the metallicity evolution of the star-forming gas across the cosmic time. We investigate the bounds on the metallicity evolution, mass distribution, and delay times of the binary BH sources based on the 10 observed events by LIGO. We parametrize ${M}_{\mathrm{BH}}^{\max }$ to be a function of metallicity that itself is modeled to evolve with redshift in either a modest or rapid fashion. Rapid metallicity evolution models predict a stringent bound of ${M}_{\mathrm{BH}}^{\max }={44}_{-5}^{+9}{M}_{\odot }$, while the bound on ${M}_{\mathrm{BH}}^{\max }$ in the models with modest metallicity evolution is ${M}_{\mathrm{BH}}^{\max }={52}_{-9}^{+16}{M}_{\odot }$. Therefore, inferring ${M}_{\mathrm{BH}}^{\max }$ from GW data depends on the assumed metal enrichment history of the universe that is not severely constrained at the moment.